Generally, display materials such as liquid crystal display devices or organic EL devices have an electrode overcoating, a planarization film, a dielectric film and the like made of an acrylic resin, a novolac resin, a polyimide resin and the like. These overcoatings, planarization films and dielectric films are formed in desired patterns by photolithography.
However, up to now, it has been difficult to obtain films which have heat resistance, transparency and adhesion while securing sufficient sensitivity during exposure and development. Further, despite their high transparency and sensitivity, alkali-soluble acrylic photosensitive resins generally have low heat resistance, and are difficult to develop with 2.38 wt % aqueous tetramethylammonium hydroxide solution usually used for photoresist development without dilution.
On the other hand, usual thermosetting photosensitive acrylic resins contain polymers having a low glass transition temperature as the base and therefore can form only patterns having a semicircular profile because reflow occurs before crosslinking. Further, it is necessary to increase the crosslinking rate above the reflow rate to obtain patterns having a trapezoidal profile. Use of a copolymer of an unsaturated carboxylic acid and an epoxy group-containing unsaturated compound facilitates thermal crosslinking and affords resin compositions which can form patterns having a trapezoidal profile by undergoing crosslinking before reflow. However, there was a problem that these resin such as compositions have poor storage stability.
The present invention has been made under these circumstances, and relates to a positive photosensitive composition capable of being developed with 2.38 wt % aqueous tetramethylammonium hydroxide solution usually used in a photoresist step, and has high sensitivity, photosensitive properties which ensure excellent resolution and excellent properties such as heat resistance, a planarization property, transparency and low water absorption. Further, the present invention provides a positive photosensitive resin composition capable of arbitrarily forming a pattern with a semicircular or trapezoidal section after curing depending on the postbake conditions, and a method for forming a pattern.